The recovered copper sulfide ore containing gold, since copper has a serious impact on the cyanidation process, after the majority of the copper beneficiation plant using a sulfur separation process are derived gold concentrate containing copper and gold concentrate sulfur, sulfur concentrate The gold is extracted by cyanidation, while the copper-bearing gold concentrate is sent to the smelter for fire treatment. The real estate gold cannot be realized, which seriously affects the economic benefits of the gold mine. Therefore, how to effectively leaching copper-bearing gold concentrate is an important issue that needs to be solved urgently in gold and copper mines.
First, the nature of raw materials
Ore sample used in the test is a copper-containing gold concentrate gold Liaoning, mainly metallic minerals chalcopyrite, pyrrhotite, pyrite, a small amount of sphalerite, galena, native gold, occasionally Copper ore, porphyrite, copper blue, limonite, etc. There is also a small amount of malachite and azurite in the ore. Gangue minerals chlorite, sericite times for, kaolin, feldspar, a small amount of quartz, hornblende, biotite. Due to the strong alteration of the ore, most of the plagioclase becomes sericite, so the gangue mineral in the slime is dominated by sericite. The main chemical components of the sample and the state of occurrence of gold in the mineral are shown in Tables 1 and 2, respectively.
Table 1 Analysis of main elements of a flotation gold concentrate
Table 2 % of gold in minerals
It can be seen from Table 1 that the gold concentrate has a high content of copper and is a major associated element and a major element affecting gold leaching.
Second, the test results and discussion
(1) Conventional cyanide leaching test
Firstly, the conventional gold cyanide leaching test was carried out on the test gold concentrate. The best experimental conditions were: grinding fineness -50μm, 85%, liquid-solid ratio 3:1, CaO dosage 4kg/t, NaCN dosage 8kg/t, The leaching time is 40h. The test results are shown in Table 3.
Table 3 Results of conventional cyanide leaching test
It can be seen from the test results in Table 3 that under the optimal conditions, the gold leaching rate of conventional cyanidation leaching is only 43.11%, indicating that copper has a great influence on cyanide leaching.
The mechanism of influence of copper minerals on cyanide leaching is as follows.
1. The reaction of soluble copper with cyanide consumes a large amount of cyanide and oxygen. Except for copper oxide which is easily soluble in cyanide solution, various copper sulfide minerals have different degrees of solubility. For example, chalcopyrite, porphyrite and sulphur arsenic ore have a solubility of more than 65% at room temperature. The dissolved chalcopyrite also has a solubility of 6% [1]. The Cu 2 + dissolved in the ore oxidizes the free cyanide in the slurry to cyanide and cyanate, and Cu 2 + becomes Cu + ; Cu + forms a copper cyanide complex with CN - , resulting in consumption of a large amount of cyanide. Compound, whose main chemical reaction is
2Cu 2 + +7CN - +2OH - →2Cu(CN) 2 - 3 +CNO - +H 2 O
It can be known from the reaction formula that the molar ratio of Cu 2 + to CN - is 1:3.5. According to this calculation, the theoretical consumption of cyanide is 2.70 times of the amount of copper, that is, each leaching of 1 g of copper in the ore is consumed. 2.70g of cyanide.
The dissolution of copper minerals in cyanide solution not only consumes cyanide, but also consumes oxygen in the solution. For example, the dissolution reaction of chalcopyrite is 2Cu 2 S+4NaCN+2H 2 O+O 2 →Cu 2 (CN) 2 +Cu 2 (CNS) 2 +4 NaOH
2. The presence of soluble copper reduces the leaching rate of gold. The dissolution of gold in the cyanidation process is
It can be seen that the oxygen concentration in the solution and the free CN- are necessary conditions for gold dissolution. First, the gold is oxidized to Au + by O2, and Au + then reacts with CN - to form Au(CN) -
2, so that gold can be dissolved. Processing copper-containing materials
When the dissolution of copper consumes cyanide ions and oxygen in the solution, the cyanide ion activity in the solution is lowered, especially after a small amount of dissolved oxygen in the solution is consumed, causing severe oxygen deficiency in the solution, resulting in gold. The leaching rate and the leaching rate are reduced.
(2) Cyanide leaching test after drug withdrawal
In order to determine the effect of the flotation agent on cyanide leaching, the sample was subjected to a cyanide leaching comparative test after drug removal. The method of de-dosing is to re-mill the concentrate and then add the desorbent X2P for 30 min. The cyanide leaching conditions of the drug-free sample were the same as those of the conventional cyanide leaching test, and the test results are shown in Table 4.
Table 4 Leaching test results after drug withdrawal
Comparing the test results in Table 4 with Table 3, it can be seen that after the gold concentrate is removed, the gold leaching rate is increased by 7.11%, indicating that the gold concentrate can improve the cyanide leaching process after drug removal. In fact, theoretical studies have found that xanthine is easy to form double xanthate on the surface of gold carrier mineral chalcopyrite, pyrite, pyrrhotite, etc., in the surface of galena, porphyrite, chalcopyrite, etc. It is easy to form metalloenolate, which has both xanthate and metalloxate on the surface of copper blue [2] , which makes the surface of gold passivate, hindering the contact between gold and cyanide, thus reducing the Gold cyanide leaching rate. After the drug is removed, the newly formed substance on the surface of the mineral is removed, which helps to increase the leaching rate of gold.
(III) Ammonia-cyanide mixed liquor leaching test
Cyanide leaching after drug removal, although the gold leaching rate has increased, but due to the influence of copper in gold concentrate, the leaching rate is still not satisfactory, only reached 50.22%. In order to further increase the leaching rate of gold in the ore, an ammonia-cyanide mixture is used as the leaching agent, and the advantages are:
(1) Ammonia can inhibit the adverse effects of copper on cyanidation. NH 3 generated with Cu 2 + copper ammonia complex ion Cu (NH 3) 2 + 4 , so that, in cyanide solution was added NH 3 reduces the activity of Cu 2 +, Cu 2 and prevents a certain extent + Degradation of cyanide caused. Because of the presence of a solution of Cu (NH3) 2 + 4, so that Cu (CN) - 2 precipitated out of solution in the form of CuCN by oxidation. When pH > 9.5, Cu 2 + precipitates Cu(OH) 2 due to the protonation of NH3 and CN - .
(2) The ammonia-cyanide mixture facilitates the leaching of gold. Ammonia - cyanide mixture, the CN - agents cyanide, Cu (NH3) 2 + 4 as oxidant gold dissolution, the reaction equation is
(3) The ammonia-cyanide mixture can reduce the consumption of cyanide. When the ammonia concentration in the leachate exceeds 0.1 mol/L, the copper cyanide ion in the solution is gradually replaced by the copper ammine complex ion, so that the non-cyanide complexing agent NH 3 can replace or partially replace the rhodium metal complex. The cyanide in the mixture increases the free cyanide in the solution.
In summary, in the Cu 2 + -CN ― NH 3 leaching system, the addition of ammonia reduces the Cu 2 + in the solution, inhibits the influence of copper on cyanidation, and produces a new cyanide agent in the solution. Cu(CN) 2 - 3 or Cu(CN) 3 - 4 , thereby increasing the oxidant Cu(NH3) 2 + 4 , which in turn increases the concentration of free cyanide in the solution, thereby facilitating the increase of gold leaching rate, and Can reduce the consumption of cyanide.
1. Ammonia dosage test
The copper-bearing gold concentrate sample after drug removal has a grinding fineness of -50 μm, 85%, a slurry solid ratio of 3:1, a CaO dosage of 4 kg/t (pH=10.5 to 11.0), and a NaCN dosage of 8 kg/t. The leaching time was fixed for 40 h, and the amount of ammonia was changed to carry out cyanidation leaching. The test results are shown in Fig. 1.
Figure 1 NH 3 dosage test results
1-Au; 2-Cu
It can be seen from Fig. 1 that the addition of ammonia greatly improves the leaching effect, the leaching rate of gold increases with the increase of ammonia dosage, and reaches the highest point when the amount of ammonia is 5.92 kg/t; the amount of ammonia continues to increase, and the leaching of gold The rate has declined. Therefore, a suitable amount of ammonia is 5.92 kg/t.
2, NaCN dosage test
Under the above cyanidation conditions, a certain ammonia concentration was maintained, that is, NH3 was 5.92 kg/t, and the amount of sodium cyanide was changed to test. The test results are shown in Fig. 2.
Figure 2 NaCN dosage test results
1-Au; 2-Cu
It can be seen from Fig. 2 that in the ammonia-cyanide mixture, when the amount of ammonia is kept constant, the amount of NaCN, that is, the CN - concentration, is increased, and the leaching rate of gold begins to increase, and then begins to decrease. This is because the increase in [CN -] after, NH3 and CN - from a relatively low concentration of the reduced inhibition of NH3 copper, copper dissolution is relatively increased, resulting in its influence on cyanide leaching is enhanced. Figure 1 and Figure 2 illustrate that there is an optimum ratio of NH3 and NaCN between 5.92:8. At this ratio, the cyanidation leaching rate of gold can be increased to 90.67%, and the amount of NH3 or NaCN can be increased arbitrarily. Not so good results.
(4) Ammonia-cyanide mixture carbon leaching test
On the basis of the above test, the ammonia-cyanide mixed liquid carbon slurry test was carried out, and the test results are shown in Table 5.
Table 5 Ammonia-cyanide mixed liquid carbon slurry test results
It can be seen from the test results in Table 5 that the leaching rate can be increased by 2.80 percentage points when the carbon leaching is directly leached. This is because the activated carbon adsorbs the dissolved gold in time, reduces the concentration of Au(CN) 2 - in the solution, accelerates the dissolution rate of gold, and thereby increases the leaching rate of gold.
Third, the conclusion
(1) Drug removal is beneficial to increase the gold leaching rate of copper-bearing gold concentrate. It is recommended to remove the drug and then use the ammonia-cyanide mixture for cyanide leaching.
(2) When treating copper-containing gold concentrate, ammonia can suppress the influence of copper on the one hand, and reduce the consumption of cyanide on the other hand, which can greatly increase the leaching rate of gold. In the cyanide leaching process, and should be kept NH3 CN - from an appropriate concentration ratio, in order to maximize the leaching rate of gold.
(3) Carbon leaching of the copper-bearing gold concentrate studied with ammonia-cyanide mixture is better than direct leaching with ammonia-cyanide mixture. Therefore, it is recommended to use carbon slurry method for ammonia-cyanide mixing. Liquid as a leaching agent.
references
[1] Cai Dianzhen, Xu Zhiming. Gold ore chemical treatment technology. Shenyang: Northeastern University Press, 1996
[2] Qiu Jicun. Mineral Processing. Beijing: Metallurgical Industry Press, 1997
Author unit
Northeastern University (Zhou Shijie, Wang Chenggong, Zhang Shumin)
Live Dragon Mining Co., Ltd. East (Lv Chang)
Port Forks,30 Ton Port Forks,42Crmo Port Forks,High Quality Port Fork
Shandong Techence Forging Co.,Ltd , https://www.shandongtechence.com